1. Field of the Invention
The present invention relates to a convergence system of broadcasting and communication that provides subscribers by converging broadcasting and communication services through optical fiber transmission lines. More particularly, the present invention relates to a connection structure between a network switch (L2 switch), such as a layer 2 for processing an IP over Ethernet that is a communication service, and a subscriber line unit (SLU) in a subscriber distribution network apparatus of a convergence system of broadcasting and communication.
2. Description of the Related Art
In general, a communication network using the Ethernet protocol comprises a packet communication network that provides the foundation for most local area networks and Internet communication networks.
A 10 Base-T is commonly employed in most of the Ethernet communication networks utilized by subscribers, which is mainly used in local area networks, companies, and schools. Recent improvements in Ethernet technology has led to a metro Ethernet communication network providing subscriber homes with 100 Mbps Internet communication services of 100 Base-T by means of an unshielded twisted pair (hereinafter, referred to as an UTP) cable.
A convergence system of broadcasting and communication that utilizes Ethernet communication networks, Ethernet equipment that multiplexes digital broadcasting streams and Ethernet data by a time division multiplexing (TDM), generates new types of digital streams, and distributes the generated digital streams to subscribers.
FIG. 1 is a block diagram of a conventional convergence system of broadcasting and communication. As shown in FIG. 1, the conventional convergence system that provides broadcasting and communication services includes an optical line terminal (hereinafter, referred to as an OLT) 100, an optical network unit (hereinafter, referred to as an ONU) 102 comprising a plurality of ONUs numbered from 1 to N, and optical cables that connect plurality of ONUs to the OLT 100. The OLT 100 receives broadcasting data from broadcasters to provide subscribers with broadcasting services by converting the data into an optical signal containing bundled components that correspond to the data, and then transmitting one tied optical signal. The ONU 102 is a user-side apparatus that send information transmitted from the OLT 100 to subscribers. When broadcasting/communication data sent from broadcasters are subsequently transmitted to the ONU 102 via the OLT 100, the ONU 102 receives the service requirements of subscribers from a set-top box 104 and then provides corresponding services.
In designing the ONU 102 functioning as an optical subscriber distribution network for the users via set-top boxes, which simultaneously provides broadcasting and communication in a convergence system of broadcasting and communication as described above, a commercial L2 switch must be used as part of the network apparatus in order to process Ethernet-based packet data for communication services.
FIG. 2 shows a structure for connecting the commercial L2 switch. The switch outputs 100 Base-T signals in the ONU providing the convergence system of broadcasting and communication, to a plurality of subscriber line units (hereinafter, referred to as a SLU) for adding broadcasting signals, which are output from broadcasting signal receivers, to Ethernet signals outputted from the L2 switch 110 (shown in FIG. 2 ).
FIG. 2 shows outside media attachment units (hereinafter, referred to as a MAU) 114 have UTP cable interfaces, as well as media converters (hereinafter, referred to as a MIC) 120 that are additionally provided in the ONU 102. Further, the L2 switch 110 is connected to SLUs 130 through the outside MAUs 114 having UTP cable interfaces and the M/Cs 120. Herein, the M/Cs 120 convert 100 Base-T signals into 100 Base-F signals in order to input the 100 Base-T signals outputted from the L2 switch 110 to the SLUs 130.
The L2 switch 110 classifies the packets and controls paths of a commercial network switch outputting the 100 Base-T signals. In general, the L2 switch 110 includes a PHY 112 (PHY is an abbreviation for physical chip), which is connected to a switch chipset 111, and MAUs 113. Each of the MAUs 113 has a connector connection portion that connects each of the MAUs 113 to the PHY 112 through a connector. In addition, each of the MAUs has a UTP cable connection portion to which a UTP cable is connected. Further, each of the MAUs 113 generates power for transmitting signals through the UTP cable.
FIG. 3 shows that each of the SLUs 130 includes a first PHY 131, a time division multiplexing (hereinafter, referred to as a TDM) 132, a plurality of transceiving modules 133, a second PHY 134 provided between each of the transceiving modules 133 and the first PHY 131, and a voltage signal conversion unit 135. The first PHY 131 converts parallel signals having a type of a media independent interface (hereinafter, referred to as a MII) into 100 Base-F signals, or which converts 100 Base-F signals into MII signals. The TDM 132 multiplexes Ethernet signals having a MII type and broadcasting signals. The voltage signal conversion unit 135 converts the multiplexed signal outputted from the TDM 132 into a differential positive emitter coupled logic (PECL) signal, which is a voltage signal having a predetermined level, and then the voltage signal conversion unit provides the PECL signal to the transceiving modules 133. The second PHY 134 converts the PECL signals provided from the transceiving modules 133 into MII signals and then provides the MII signals to the first PHY 131.
In designing the ONU 102 by means of the L2 switch to process Ethernet-based packet data for communication services, the ONU 102, which is an optical subscriber distribution network apparatus for simultaneously providing broadcasting and communication, must include a MAU 114 and a M/C 120 in order to connect the L2 switch with the SLUs 130. The MAU 114 has an UTP cable connection portion and an RJ-45 connector connection portion, and the M/C 120 is used for converting 100 Base-T signals into 100 Base-F signals.
As described above, the commercial L2 switch has an UTP cable interface. Therefore, when the commercial L2 switch is used, it is necessary to provide separate apparatuses for the UTP cable interface between the commercial L2 switch and the SLUs. Further, when one subscriber distribution network comprises a system for providing services to several hundred subscriber (400˜500 subscribers), a plurality of UTP cables are used for connecting the L2 switch to the plurality of SLUs. Therefore, the structure of the system becomes more complicated and the volume of the system increases, thereby having difficulties in providing an efficient subscriber distribution network.